This invention relates to surgical sutures coated with a coating material to improve fiber lubricity. More particularly, this invention relates coated surgical sutures which exhibit improved tie-down performance without a corresponding loss in knot security.
Suture materials are classified as either absorbable or nonabsorbable, and are considered to be absorbable if they disappear from the sewn tissue within a year after surgery. The most commonly used absorbable suture materials are catgut and extruded collagenous materials. More recently, absorbable sutures derived from certain synthetic polymers have been developed and used. Typical of synthetic absorbable polymers used as suture materials are glycolide homopolymer and glycolide-lactide copolymer. Synthetic absorbable materials are generally stiffer than their catgut counterpart, and synthetic absorbable sutures are therefore usually employed in a braided, multifilament construction in order to obtain desired softness and flexibility. Other materials such as polyethylene terephthalate and nylon are also employed in a braided construction as non-absorbable suture materials.
Whether absorbable or non-absorbable, synthetic braided multifilament sutures show a certain degree of unsatisfactory roughness or grabbiness in what has been termed their "tie-down" performance, i.e. the ease of sliding a knot down the suture into place. An important handling characteristic of sutures, however, is that they slide easily into place during the knotting process. Contrasted with the ease of knot placement is the ability of the knot to hold the suture, sometimes hereinafter referred to as the property of knot security. While it is desirable that surgical knots easily slide into place and tie, it is also extremely important that the knot hold for an acceptable length of time. Consequently, a number of methods have heretofore been employed in an attempt to improve these two particular characteristics of the suture.
Surface coating is the principal method which has been employed to improve tie-down performance. Commonly used coating materials include paraffin wax, beeswax and silicone oil. Other coating materials which have been used for the improvement of tie-down performance are disclosed, for example, in U.S. Pat. Nos. 4,047,533, 4,201,216, 4,185,637, 4,105,034, 3,942,532, 4,532,929, 4,027,676 and 4,711,241. In addition, the inventor of the instant invention has disclosed a coating composition comprising sucrose fatty acid ester for improving the tie-down performance of sutures in a pending patent application, U.S. Serial No. 153,996.
Although there has been some improvement in the tie-down performance of sutures including the coating compositions known in the art, the coating compositions have also resulted in a decrease in knot security. The problem of knot loosening has therefore increased, which is a particularly undesirable result.
In addition to the attempts at improving the tie-down performance of sutures, means for improving knot security have also been heretofore suggested. One method to improve knot security is to texture the yarn fibers used to form the suture. Textured yarn braided multifilament sutures are disclosed, for example, in Japanese Utility Model Application Laid-Open No. 62-97648 and No. 62-97649. These sutures are not coated and do not exhibit a tie-down performance as good as that exhibited by coated sutures.
The inventors of the present invention have found that although sutures with either improved tie-down performance or knot security are known in the surgical arts, braided multifilament sutures having the aforementioned two characteristics are not presently known.